From The Viewpoint Of An Alien Astronomer, How Does Jupiter Affect Observations Of Our Sun

Astronomy Exam 3

How does the Sun’s mass compare with that of the planets?

It is a thousand times more massive than all the planets combined.

Which planet has a ring system?
Jupiter
Saturn
Uranus
Neptune
All of the above

all of the above

Which planet could an astronaut visit without the need for a spacesuit (and survive)?
Mercury
Venus
the Moon
Mars
None; an astronaut would need a spacesuit to survive a visit to any other planet in the solar system.

None; an astronaut would need a spacesuit to survive a visit to any other planet in the solar system.

What are the main constituents of the jovian planets?

hydrogen and helium

Some astronomers suggest that, rather than being a planet, Pluto is really just a large member of

Kuiper belt

Why did the solar nebula heat up as it collapsed?

As the cloud shrank, its gravitational potential energy was converted to thermal energy.

What percentage of the solar nebula’s mass consisted of hydrogen and helium gases?

98%

Approximately how many other planetary systems have been discovered to date?

100

How many of the planets orbit the Sun in the same direction as Earth does?

all

Planetary orbits in our solar system are:

fairly circular and in the same plane.

The composition of the solar nebula was 98%

hydrogen and helium

Are there any exceptions to the rule that planets rotate with small axis tilts and in the same direction as they orbit the Sun?

Venus and Uranus are exceptions.

Leftover ice-rich planetesimals are called

comets.

What’s unusual about our Moon?

It’s surprisingly large relative to the planet it orbits.

About how old is the solar system?

4.5 billion years

On average, Venus has the hottest surface temperature of any planet in the solar system.

true

Our Moon is about the same size as moons of the other terrestrial planets.

false

The weather conditions on Mars today are much different than they were in the distant past.

true

Moons cannot have atmospheres, active volcanoes, or liquid water.

false

Saturn is the only planet in the solar system with rings.

false

Neptune orbits the Sun in the opposite direction of all the other planets.

false

If Pluto were as large as the planet Mercury, we would classify it as a terrestrial planet.

false

Asteroids are made of essentially the same materials as the terrestrial planets.

true

When scientists say that our solar system is about 4 billion years old, they are making a rough estimate based on guesswork about how long it should have taken planets to form.

false

Is carbon-14 useful for establishing Earth’s age? Why or why not?

Carbon-14 is not useful for establishing the age of Earth because its half-life is too short in comparison to Earths age

Rank the five terrestrial worlds in order of size from smallest to largest:

Moon, Mercury, Mars, Venus, Earth.

Spacecraft have landed on all the terrestrial worlds except:

mercury

Which of the following worlds has the most substantial atmosphere?

venus

What do we mean by a runaway greenhouse effect?

a greenhouse effect that keeps getting stronger until all of a planet’s greenhouse gases are in its atmosphere

How do typical wind speeds in Jupiter’s atmosphere compare to typical wind speeds on Earth?

They are much faster than hurricane winds on Earth.

What atmospheric constituent is responsible for the blue color of Uranus and Neptune?

methane

Which of the following statements about the moons of the jovian planets is NOT true?

Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids.
Many of the moons are made largely of ices.
Some of the moons are big enough that we’d call them planets (or dwarf planets) if they orbited the Sun.
One of the moons has a thick atmosphere.

Most of the moons are large enough to be spherical in shape, but a few have the more potato-like shapes of asteroids.

Which statement about Io is true?

It is the most volcanically active body in our solar system.

Which moon has a thick atmosphere made mostly of nitrogen?

Titan

Suppose you could float in space just a few meters above Saturn’s rings. What would you see as you looked down on the rings?

countless icy particles, ranging in size from dust grains to large boulders

Which moon is considered likely to have a deep, subsurface ocean of liquid water?

europa

A rock found on Earth that crashed down from space is called _________.

meteorite

The asteroid belt is located _________.

between the orbits of mars and jupiter

Which of the following statements about asteroids, Kuiper belt objects, and Oort cloud objects is true?

Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not.

Which direction do a comet’s dust and plasma tails point?

generally away from the sun

According to current evidence, Pluto is best explained as ______.

a large member of the Kuiper belt

Which moon shows evidence of rainfall and erosion by some liquid substance?

titan

Io experiences tidal heating primarily because __________.

Io’s elliptical orbit causes the tidal force on Io to vary as it orbits Jupiter

From Part A, Io’s elliptical orbit is necessary to its tidal heating. This elliptical orbit, in turn, is a result of the orbital resonance among Io, Europa, and Ganymede. This orbital resonance causes Io to have a more elliptical orbit than it would otherwise, because __________.

Io periodically passes Europa and Ganymede in the same orbital position

We cannot see tidal forces or tidal heating; rather, we predict that they must occur based on the orbital characteristics of the moons. What observational evidence confirms that tidal heating is important on Io?

active volcanoes on Io

The orbital resonance also gives Europa an elliptical orbit, so it also experiences tidal heating. However, Europa experiences less tidal heating than Io, because Europa __________ than Io.

is farther from jupiter

We now know of many Jupiter-size planets around other stars. Suppose that future observations show that one of these planets has two orbiting moons. What additional information, if any, would we need to decide whether these moons experience tidal heating?

we need to know their orbital periods

Saturn’s rings are composed of __________.

lots of individual particles of ice and rock

Saturn’s rings look bright because __________.

light from the Sun reflects off the material in the rings

Which of the following statements correctly describes the motion of the particles in Saturn’s rings?

Particles in the inner rings orbit Saturn at a faster speed than particles in the outer rings.

The main ingredients of most satellites of the jovian planets are

hydrogen compound ices.

Some jovian planets give off more energy than they receive because of

ongoing contraction or differentiation.

Why does Neptune appear blue and Jupiter red?

Methane in Neptune’s atmosphere absorbs red light.

The asteroid belt lies between the orbits of

mars and jupiter

Did a large terrestrial planet ever form in the region of the asteroid belt?

No, because Jupiter prevented one from accreting

How big an object causes a typical shooting star?

a grain of sand or a small pebble

Which are thought to have formed farthest from the Sun?

Kuiper belt comets

A comet entering the inner solar system from afar will __________.

form a coma and some time later form a tail

During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________.

sunlight reflects off the comet’s tail and coma

A comet’s plasma tail always points directly away from the Sun because __________.

of pressure exerted by the fast-moving charged particles in the solar wind

What does Pluto most resemble?

a comet

From the viewpoint of an alien astronomer, how does Jupiter affect observations of our Sun?

It causes the Sun to move in a small ellipse with an orbital period of about 12 years.

Suppose you are using the Doppler method to look for planets around another star. What must you do?

Compare many spectra of the star taken over a period of many months or years.

In general, which type of planet would you expect to cause the largest Doppler shift in the spectrum of its star?

a massive planet that is close to its star

Suppose a planet is discovered by the Doppler method and is then discovered to have transits. In that case, we can determine all the following about the planet except __________.

its rotation period

The transit method allows us in principle to find planets around __________.

only a small fraction of stars that have planets

You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?

The planet must be closer to the star than Earth is to the Sun.

Which of the following will allow you to learn something about a transiting planet’s atmospheric composition?

Compare spectra obtained before and during an eclipse.

Very few of the known extrasolar planets have sizes as small as Earth. The most likely reason for this fact is that __________.

small planets are more difficult to detect than larger planets

Based on everything you have learned about the formation of our solar system, which of the following statements is probably not true?

Only a tiny percentage of stars are surrounded by spinning disks of gas during their formation.

To date, we’ve found very few planets orbiting their stars at distances comparable to the distances of the jovian planets in our solar system. Why do astronomers think this is the case?

We have not yet been searching for planets at such distances for a long enough time.

Current evidence suggests that some massive jovian planets orbit at very close orbital distances to their stars. How do we think these planets ended up on these close orbits?

These planets migrated inward after being born on orbits much farther from their stars.

Assuming that our ideas about how “hot Jupiters” ended up on their current orbits are correct, why didn’t our own solar system end up with any hot Jupiters?

Our solar nebula must have been blown into space shortly after the formation of the jovian planets.

When is the soonest we are likely to have moderate-resolution images and spectra of Earthlike planets around other stars?

In a decade or two, through space observatories now in the early planning stages.

What is an extrasolar planet?

A planet that orbits a star that is not our own Sun

The first confirmed detections of extrasolar planets occurred in ____________.

the 1990’s

What do the astrometric, Doppler, and transit methods share in common?

They all search for planets by measuring properties of a star rather than of the planets themselves.

The astrometric method looks for planets with careful measurements of a star’s _________.

position in the sky

In essence, the Kepler mission searched for extrasolar planets by ____________.

monitoring stars for slight dimming that might occur as unseen planets pass in front of them

Can we determine orbital distances for extrasolar planets using the astrometric, Doppler, or transit methods?

Yes: All three methods give us direct information about a planet’s orbital period, from which we can use Newton’s version of Kepler’s third law to calculate the planet’s distance.

Why do we say that the Doppler method gives a planet’s “minimum mass”?

The size of the Doppler shift that we detect depends on the tilt of a planet’s orbit.

Which of the following statements is not true about the planets so far discovered around other stars?

Photographs reveal that most of them have atmospheres much like that of Jupiter.

What do we mean by a “hot Jupiter”?

a planet that is Jupiter-like in size but orbits very close to its star

Overall, what do current data suggest about planetary types in other planetary systems?

Planets come in a wider range of types than the planets in our solar system.

Based on current data, about what fraction of stars have one or more planets?

at least about 70%

Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?

Jovian planets can migrate from the orbits in which they are born.

Which of the following might explain the lack of “water worlds”—small planets made mostly of water or other hydrogen compounds—in our own solar system?

In our solar system, the solar wind did not clear out gas until relatively late.

How is the GAIA mission relevant to the search for extrasolar planets?